@article{IM_1988__93_2_143593,
     author = {Harold Donnelly and Charles Fefferman},
     title = {Nodal sets of eigenfunctions on {Riemannian} manifolds.},
     journal = {Inventiones mathematicae},
     pages = {161--184},
     publisher = {mathdoc},
     volume = {93},
     number = {2},
     year = {1988},
     zbl = {0659.58047},
     url = {http://geodesic.mathdoc.fr/item/IM_1988__93_2_143593/}
}